Challenges in the Management of a Difficult-to-Treat Patient With Hairy Cell Leukemia: A Case Report.

Hairy cell leukemia (HCL) is a rare, chronic B-cell malignancy with an indolent course that typically responds well to purine nucleoside analogs, such as cladribine. We present the case of a 74-year-old woman with nearly three decades of recurrent HCL, marked by multiple relapses and significant toxicities to various treatments, including purine analogs, BRAF inhibitors, BTK inhibitors, a cytoreductive agent, and the monoclonal antibody rituximab. Despite severe allergic reactions and intolerances to standard therapies, the patient achieved multiple remissions. This case underscores the challenges in managing treatment-resistant HCL and highlights the need for personalized treatment strategies in patients with relapsed disease and drug toxicities.